PROJECT SUMMARY Mammalian skin provides a critical barrier function that protects the body from desiccation thereby, in the case of humans, permitting terrestrial life. Furthermore, beyond this water barrier function, the epidermal barrier protects the body from external insults while simultaneously being the primary interface between the body and the external environment. The Barrier Function of Mammalian Skin Gordon Research Conference has, for the last 30 years, focused on scientific topics broadly related to furthering our understanding of the processes which underline skin barrier function in health and disease. In addition to its biological and biophysical focus, a key differentiating aspect of this conference has, and continues to be, the inclusion of new scientific understanding and technology associated with the topical delivery of medicines into and through the skin barrier. There is no equivalent multidiscipline epidermal barrier conference and, as such, this conference plays a vital role in bringing together scientists, clinicians, and engineers to collaborate in advancing our understanding of epidermal barrier science, and to collaborate in the development of physical, chemical and biological technologies to improve epidermal health. The overarching theme of the 2019 conference is Barrier Function of Mammalian Skin: Insights from In Silico Models to In Vivo Pathology which will bring together scientific leaders from the diverse community of researchers working on the epidermal barrier. This will include those developing in silico molecular simulations of the stratum corneum, new experimental cell and tissue models, and finally those characterizing the in vivo pathological changes in skin barrier function associated with skin and systemic disease. The major themes of the 2019 conference program will be: 1) New Developments in Skin and Epidermal Equivalent Models; 2) In Silico Modeling of the Skin Barrier and Permeation Pathways; 3) Spontaneous and Man-made Animal Models of the Epidermal Barrier; 4) Changes in Epidermal Barrier Function and Health Associated with Systemic Disease; 5) Predicting, Measuring and Modeling Topical Drug Delivery; and 6) News and Controversies in Epidermal Barrier Science. While the above themes define the program agenda, as in previous years the program will include a session of short oral presentations selected from the conference posters. Bringing together this community of students, scientists, clinicians, and engineers to share the most recent insights and understanding of skin barrier science from their respective disciplines. The learnings shared at this conference, and the interactions between attendees, will encourage multi-disciplinary collaborations focused on the shared goal of understanding epidermal barrier function to improve health locally, in the skin, and systemically.